The invention relates to tubeless pneumatic tires and wheels, and more specifically, to a wheel configured to allow hand mounting of a tubeless pneumatic tire on the wheel without the assistance of tools.
Tubeless pneumatic tire and wheel assemblies form a chamber that retains air without a separate air-holding tube. Tension of the tire beads on the wheel bead seats forms an air-tight seal. Internal air pressure acts axially outward to push the tire bead against the wheel rim flange. The rim flange, which extends radially outward from the bead seat, prevents the tire bead from coming off the wheel.
In mounting pneumatic tire on a wheel, typically, one bead is entirely passed relatively easily over the rim flange. Mounting the other bead is assisted by the wheel well, which allows a portion of the bead to slip over the flange, but requires the application of force to move the remaining portion of the bead over the flange. This step requires tools and typically requires a machine because the tire bead must be deformed from a circular shape and stretched to pass over the rim flange.
The present invention is directed to a pneumatic tire and wheel having geometries specifically adapted to allow the tire to be mounted on the wheel by hand without the use of tools or machines.
More particularly, the present invention is directed to a wheel having a rim flange of a height and having a well with a depth relative to the rim flange height and at a location relative to the rim flange that permits a tire bead to pass over the rim flange with manually-generated forces.
According to the invention, for a tire having a bead seat circumference Ct, the wheel geometry is defined by:       C    t    =                    1        2            ⁢      π      ⁢                           ⁢              D        w              +          2      ⁢                                                  1              2                        ⁢                          D              w              2                                +                                    D              w                        ⁡                          (                              G                +                H                            )                                +                                    (                              G                +                H                            )                        2                    +                                    (                              W                +                Y                            )                        2                                +    M  where Dw is the wheel well diameter, G is the depth of the wheel well measured from the wheel bead seat, W is a axial distance from the edge of the wheel well to the mounting side flange, H is the radial height of the rim flange above the wheel bead seat, Y is the axial width of the rim flange, and M represents a quantity of extra length needed to enable hand-mounting, the units of measure being millimeters.
Preferably, the tire has beads that have an ovalization stiffness, that is the ability to resist being deformed from a circular shape to an oval shape, of not more than about 0.7 N/mm.
In addition, it may be necessary to modify the tire and/or the wheel to ensure an appropriate balance between the internal pressure of the tire and axial resistance force provided by the rim flange. A method for checking the relative forces could include the following steps. Once the rim flange height H is determined from the above relationship, the stress on the rim flange and the axially outward acting force generated by internal tire pressure may be approximately related by the following equations:   F  =      π    ⁢                   ⁢          P      ⁡              (                                            (                                                D                  eq                                2                            )                        2                    -                                    (                                                D                  b                                2                            )                        2                          )            
where, F is the axially outward acting force on the tire rim flange, Deq is the equilibrium diameter of the tire, Db is tire bead diameter, and P is the inflation pressure, andF≈σπDbH
where, σ is the stress on the tire rim flange and H is the height of the rim flange as determined from the wheel geometry equation.
To arrive at the appropriate balance of forces, the rim flange of the wheel could be reinforced to improve the handling of stresses. Alternatively, the tire could be modified, for example, the internal pressure specification P could be lowered, or the tire equilibrium diameter could be changed by reducing the aspect ratio of the tire, that is, using shorter sidewalls.